Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Using SharpCap's Polar Alignment feature
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bbbigca
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Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by bbbigca » Mon Aug 17, 2020 12:43 am

Hi all,

I have been using my Celeron Evolution 8 mount with a wedge, manually aligning with its handset or its PC software CPWI. I am interested in using SharpCap's Polar Alignment (SCPA) feature to automate my alignment, vs. buying Celestron's StarSense Autoalign.

What I am puzzled about, is how SharpCap's alignment would work in conjunction with Celestron's own alignment...? In other words, would Celestron's CPWI be aware of SCPA's alignment settings, so that I can then use CPWI to slew to a target? Would I be able to Save and Load alignment in CPWI after SCPA?

My question is due to my ignorance around where the alignment data is kept in memory. I would think that it would be logical to store alignment data in the mount itself, but I get the impression that the settings get saved to the software that performs the alignment (i.e. handset, or CPWI), and they aren't interoperable?

Please help me better understand - much appreciated!

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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by admin » Mon Aug 17, 2020 6:30 pm

Hi,

so there are two types of alignment going on here – firstly polar alignment gets your RA axis aligned properly with the Earth's rotation. Secondly there is what we might call a star alignment stage which is where your mount learns the mapping between RA and declination coordinates in the sky and the same coordinates in its own movements.

SharpCap takes over the first stage – getting the polar axis lined up. I presume that you can just skip that stage in the CPWI software and move on to the star alignment stage which SharpCap wouldn't be involved in. Note that the measurements that are made in the star alignment stage on many mounts will allow the software to compensate (at least in part) for any problems with the polar alignment or with cone error. My experience is that while that works to a degree, having the polar alignment just right and any cone error eliminated does help lead to better accuracy in go to movements.

Maybe someone who also uses the CPWI software and SharpCap's polar alignment will be able to comment further.

Cheers, Robin

bbbigca
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by bbbigca » Mon Aug 17, 2020 11:56 pm

Hi Robin,

Thanks for your prompt feedback. Yes, I realize polar alignment isn't going to do what I'm trying to do. That said, I am also finding that there are software that will allow me to also automate star alignment e.g. KStars (https://rasc-vancouver.com/2020/01/10/p ... alignment/). I imagine SharpCap could be updated to also support automated star alignment in the future?

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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by tmyers » Tue Aug 18, 2020 2:23 pm

I am curious as to how any software program is going to adjust your Altitude and Azimuth knobs for you. They may tell you which direction and how far in Minutes and Seconds it has to be moved, but can't turn the knobs for you. Adjusting the Alt and Az is the only way to physically Polar align.
Tim

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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by admin » Tue Aug 18, 2020 6:00 pm

Hi folks,

I must admit that I haven't got any plans to add functionality for the star alignment into SharpCap – that is usually fairly well handled by other software applications or even hand controllers, whereas with polar alignment it was a real struggle to find software that was both accurate and usable in the days before the SharpCap polar alignment functionality.

@Tim - I suppose you could imagine the altitude and azimuth adjustments being motorised – I'm not sure that there are any mounds where this is actually available as a feature though. Once you get to the point where that sort of feature makes sense as the best thing to add to amount you are properly at the price point where most people are going to be building observatories anyway.

Cheers, Robin

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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by bbbigca » Fri Aug 21, 2020 4:14 am

admin wrote:
Tue Aug 18, 2020 6:00 pm
I must admit that I haven't got any plans to add functionality for the star alignment into SharpCap – that is usually fairly well handled by other software applications or even hand controllers, whereas with polar alignment it was a real struggle to find software that was both accurate and usable in the days before the SharpCap polar alignment functionality.
Most star alignment requires manually locating/centering stars, which is PIA when you have an AP-only setup (that especially lacks absolute encoders). Since SharpCap's PA feature requires/uses a ~200mm scope+camera anyway, it would be great to also re-use that hardware for automated star alignment. Wouldn't it be a small extension of the Plate Solving feature (https://www.sharpcap.co.uk/sharpcap/fea ... te-solving)?

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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Post by admin » Fri Aug 21, 2020 8:36 pm

Hi,

not really – the polar alignment feature in SharpCap is very much focused about dealing with stars near the celestial pole and makes a number of assumptions in the mathematics that are only valid if you don't stray too far away from the pole. Additionally, only caring about things within about 5° of the pole means that the star database doesn't need to be very large.

I think the sort of automated steps that you are wanting to run could be easily handled by the sequencing tool that will be available in the next version of SharpCap – basically you could have a sequence where SharpCap would go to each coordinate in a pre-determined list and once the GOTO was complete it would do a plate solve (using something like Astap or AstroTortilla) and then synchronise the mount to the solved coordinates. I think that would have the effect that you're looking for.

Cheers, Robin

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